<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <button onclick="alert(2+5);">行内</button>

    <!--嵌入-->
    <button onclick="sum()">嵌入</button>

    <!--外部嵌入-->
    <button onclick="sum1()">外部引入</button>

    <a href="http://www.baidu.com" onclick="return confirm('跳转至百度')">百度一下</a>
</body>
</html>
<script>
    function sum() {
        alert(5+5);
    }
</script>
<!--外部引入-->
<!--不能以单标签结束-->
<script src="js/day5_02.js"></script>